Sensor arrangements for laser machine tools are known, for example through DE 199 06 442 A1. Insulators are a component of sensor arrangements and have become known through their use in commercially available laser processing machines.
Known insulators consist of ceramic material, such as Al2O3 for example, which has a high resistance to heat and to impacts, but can be machined only with difficulty owing to its hardness. In the case of this type of insulator, the capacitive reactance is more important than the insulation with respect to direct current. This is why a large insulating distance has to be selected in the case of an Al2O3 insulator.
During cutting, the insulator is affected by diffusely back-reflected radiation. It is therefore moreover necessary for the insulator to consist of a material that is not destroyed or damaged by the back-reflection. Al2O3 has ideal properties for this purpose since it is very resistant to heat and impact. The drawback of these insulators, however, is the fact that Al2O3 is complicated and expensive to manufacture.
Prior art conforming to the genre is disclosed in DE 40 35 404 A1. This publication relates to a nozzle for a tool for material processing. Inside, the known nozzle comprises a conical nozzle body having a tip region of brass positioned towards the workpiece and having a surface-anodised and accordingly electrically non-conductive remaining region at the side of the tip region remote from the workpiece. For fixing purposes, the nozzle body is subject to the action of a clamping element. This has an inner body of, for example, steel, as well as an outer body of electrically insulating material surrounding the inner body. The inner body of the clamping element is supported at the remaining region of the conical nozzle body at the end remote from the tip region of the conical nozzle body. The remaining region of the conical nozzle body is offset towards the workpiece with respect to the electrically insulating outer body of the clamping element. The remaining region of the conical nozzle body and the outer body of the clamping element are parts of an insulator, by means of which a nozzle electrode of the known nozzle on the workpiece side is electrically insulated against the rest of the material-processing device into which the nozzle is screwed.